130 MOEPHOLOGY AND EVOLUTION
Chimpanzees it was 4,200 mm. Hence the sexual differences in the palatal areas, like the cranial capacities, are more marked in the Gorilla. The posterior part of the palate shows variations.
The palatal processes of the palate bones may not unite, thus giving rise to a cleft palate; or the vorner or maxilla may separate the plates. The tuber maxillare may be large, and the posterior nasal spine occurs in about thirty-three per cent of skulls.
The pterygoid region varies considerably. The external pterygoid plate is small, and frequently exhibits a ridge, fossa, or pterygo-spinous foramen on its outer side. The hamular process on the internal pterygoid plate is slender and tapering, or replaced by a quadrate mass of bone. The scaphoid fossa may be very long.
The glenoid fossa is shallow, and there is a small endoglenoid process. The mastoid processes, which are definite and not represented by a rough ridge as in the Chimpanzee, are cellular with a thin wall. Owen (374) considered that the contemplation of this feature alone would lead the observer to conclude that the Gorilla may adopt the erect posture frequently, and comes nearer to Man than the other Anthropoids. The tympanic process has a vaginal ridge, and in some cases there is a distinct vaginal process as in Man. The styloid process is small.
The occipital condyles are frequently entire, but in some cases they are divided by longitudinal or transverse fissures. And a third occipital condyle appears occasionally. There may be as many as three anterior condyloid foramina.
Interior of the SkulL—The olfactory fossa is